I.S Terminals 1

[Ahr35181]

Our site installation instructions require I.S terminals to have of 50mm clearence from the side of a metal enlosure (which itself is bonded to plant earth)

Is this required in European or IEC standards?

Thanks,

Alan

 

[castera]

yes this is a requirement of EN 50020 IEC 60079-3. These clearances also apply to the spacing between the AC power terminals and the 'i s' output terminals of a module and to the spacing on a terminal rail between 'i s' circuits and any other power terminals.

regards AC

 

[Ahr35181]

castera,

Thanks for your reply, I was tring to find this in BS EN 60079 but this standard only quotes the 50mm clearence distance between I.S & non I.S terminals as you have mentioned.

Regards,

Alan

 

[castera]

Sorry your right i'm wrong the 50mm is between the parts stated above but not to earth, the only mention of clearances to earth are:- Quote " The clearance distance from bare conducting parts of external conductors connected to a terminal, to any earthed ( or other conducting parts )shall not be less than 3.0mm "

Regards AC

 

[Ahr35181]

Thanks Castera,

I've looked in an old version of BS EN 50020 & noticed the 3mm requirement. I allso noticed the minimum distance between I.S terminals of different loops is 6mm. I'm certain I heard recently that this has since been reduced in newer standards, would you know if this is the case?

Thanks,

Alan

 

[castera]

My 2003 CompEx toolbox guide quotes " Clearance between bare conducting parts or terminals of separate intrinsically safe circuits is to be no less that 6mm for all voltages up to 90 Volts peak.